This invention relates to apparatus for making envelopes from a continuous film sheet.
It is known to automatically and continuously make a large number of envelopes from a continuous film sheet by unwinding a continuous film from a film roll, slitting the continuous film sheet into two continuous strips, superposing the two slitted strips on each other, heat-sealing the superposed strips in lengthwise and transverse directions to form a plurality of rectangular sections defined by heat-sealed sides, and slitting and cutting the heat-sealed sheet into separated envelopes having their respective three heat-sealed edges. Usually a continuous film sheet is fed with its width being kept in a vertical direction to a slitting station where the continuous film sheet is slit into two continuous strips which are then superposed on each other with their planes of extension being substantially horizontally kept for heat-sealing operation. In order to unwind a continuous film sheet so as to keep its width in a vertical direction, the axis of the film roll must be supported vertically. The vertical support of the film roll axis is unstable and makes it difficult to smoothly unwind a continuous film sheet from the roll. Another disadvantage of the vertical support of the film roll axis lies in the fact that it is extremely difficult to adjust the position of the film roll during the unwinding operation in such a manner that the center line of the unwound film sheet is always maintained so as to be aligned with the level of the slitting knife which is supported at a fixed position for slitting the film sheet.
One of the objects of the invention is to provide an improved system for making envelopes from a continuous film sheet in which the above mentioned defects and disadvantages of the prior art can be avoided.
Another object of the invention is to provide a new system for supplying a continuous film sheet from a film roll to a slitting station for slitting the film sheet into two continuous strips in which the film roll axis is horizontally supported while in the slitting station the film sheet supplied has its width in a vertical direction.
A further object of the invention is to provide an improved means for shifting the film sheet during the feeding operation so that the center line of the film sheet supplied is always maintained so as to be aligned with the level of the slitting knife mounted in a fixed position.
A still another object of the invention is to provide an improved heat-sealing system for making envelopes from a continuous film sheet whereby undesirable deformation of the heat-sealed product due to the greater heat shrinkage on one surface thereof can be avoided.
Other objects of the invention will partly be apparent and partly become clear from the following detailed description.